feat(lotus): report the local mic level to the host (cinny #146)

The host had only a boolean `speaking` for yourself, throttled to 500 ms, so
nothing on the call bar showed that the mic was actually picking you up.

- lotusMicLevel.ts: one shared local mic sampler (a clone of the published
  track, ~10 Hz RMS, while a mic is published, muted or not), shared per
  call view model so there is one AudioContext.
- MicLevelQuantizer: 0–3 bars (≈ −46/−36/−26 dBFS), rising at once and
  falling one bar per sample so it doesn't flicker between words.
- fromWidget io.lotus.mic_level { bars } only when the value changes; 0 while
  muted or with no mic. Opt-in with the host state stream (lotusCallState=1).
- "Talking while muted" (#37) now reads the same sampler instead of running
  its own; same gate and behaviour.

Verified in a local call with a fake-tone mic: the host receives 0–3 as the
tone rises/falls (about 4 messages/s while it changes), 0 on mute and levels
again on unmute; muted + tone still raises speakingWhileMuted and the host's
"You're muted" notice. Lotus/room suites pass on Node 22 (148 tests).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/lotus/lotusActions.ts

@@ -80,6 +80,11 @@ export enum LotusWidgetActions {
    * them. Its arrival also tells the host this fork supports the actions above.
    */
   ControlsState = "io.lotus.controls_state",
+  /**
+   * fromWidget: local mic level `{ bars: 0 | 1 | 2 | 3 }` (cinny #146), sent
+   * only when it changes (≤ 10 Hz); 0 while muted or with no mic.
+   */
+  MicLevel = "io.lotus.mic_level",
 }
 
 /** toWidget Lotus actions that must be allow-listed in `initializeWidget`. */